This invention relates to means for and methods of mixing and activating or inverting polymers, at a high speed, and in either batch or continuous loads, while being able to control, select and maintain polymer concentration and activation.
The term "activation" is widely used to describe the chemical transition of polymer to a usable form. Recently, the terminology has tended to focus on how much activation has occurred with some arguing that there must be 100% activation before the word can be used. Since nothing is ever perfect, it is seen that if this argument is carried to the extreme, very little polymer would ever be 100% activated. As used herein, no such fine level of distinction is made. The word "activated", in its many forms, is intended to encompass the start of the process and everything occurring thereafter. Perhaps the word "inversion" might be more appropriate since it applies regardless of the degree of completion of the activating process.
Liquid or emulsion polymers are ionic-charged organic molecules which are soluble in water or another electrolytic fluid, which are herinafter simply called "water". Unactivated or neat polymers are encased by an oil carrier. In this phase, the molecule is coiled upon itself in a microgel form suspended in the oil carrier. Due to its charge, it tries to uncoil, but the oil carrier overcomes the charge and keeps it coiled.
Liquid polymers are used by various industries to simplify their industrial processes and make them more economical. For example, liquid polymers may be used for water purification and flocculation; may be used in automotive paint spray booths; may be used in the chemical industry to separate inorganics and solids from plant effluent; may be used in the coal industry to promote solids settling and to float coal fines; may be used in the petro-chemical industry to enhance oil recovery; may be used in the phosphate industry to improve recovery; may be used in the pulp and paper industry as dewatering aids and retention aids; or may be used in the steel industry to settle wastes. Those familiar with this art will readily perceive many other uses in many other industries.
Usually polymers are manufactured and shipped in a deactivated form to a location where they will be used. At that location, it is necessary to activate or invert the polymers before they can be used. Usually, that means that a polymer must be mixed with water or other electrolyte (solvent), or with a chemical, to provide an electrolyte which can change the polymer from an inactive state into an active state which can be so mixed. The process for so converting the polymer into an active state is one of imparting a sufficient amount of energy to the polymer. Reference may be made to U.S. Pat. Nos. 4,057,223, 4,218,147 and 4,217,145 for examples of prior art polymer activating systems.
The polymer encased in the oil phase is inactive. Therefore, its hydrocarbon surroundings must be emulsified or broken to allow the ionic molecule to uncoil or hydrate. This process of hydration is called activation or inversion. The way in which emulsion polymers are activated are to dilute them with water and to add enough mixing energy to emulsify the oil carrier and thus to enable the ionic charged molecule to uncoil. More particularly, the energy imparted to the inactive polymer includes a mechanical agitation which breaks down the hydrocarbon carrier phase, and thus enables water to reach and react with the long coiled molecule. Once that molecule is in water, like charges on the molecule repel each ocher and the molecule straightens and changes from the coil into a long and more or less straight "conformation". Until this conformational rearrangement occurs, the molecule is useless for most purposes.
The exact amount of energy required for an emulsion polymer activation is not known. However, there is an increase in the viscosity of the polymer, which is proportional to its stage of activation. This increase in viscosity is due to the uncoiled molecules intertwining with each other. The uncoiling of the molecules provide active sites for the attachment of foreign material in a medium. Then, the increased weight on these molecules settles them, carrying with them the settled material.
In the utilization of emulsion polymers, care must be taken to properly prepare the polymer. Different polymers require different amounts of energy for activation, tougher polymers require more force, while others need less force. Further, care must be taken not to overshear the molecules. Overshearing tends to break the uncoiled molecules, thus lowering their viscosity and making them less effective. Undershearing also is deleterious in that the polymer is then inefficient and uneconomical.
The known activating systems have required relatively long periods of time (such as an hour or so) in order to, for example, complete the inversion of the polymer. This long period of time increases the requirements for holding tanks during activation. Therefore, the relatively long period of activation time is relatively expensive. Also, the requirement for such a long term for activation greatly increases the capital requirements for the purchase of machinery when a system is operating continuously, as opposed to a batch system. Thus a faster polymer activating system is highly desired.
Primarily, the prior art used the batch method to invert liquid polymers. Polymer and water are delivered to a common mixing tank. Once in the tank, the solution is beat or mixed for a specific length of time in order to impart energy thereto. After mixing, the resulting solution must age to allow enough time for the molecules to unwind.
There are many different kinds of polymers which leads to a plethora of application requirements. It might be easy to build an entirely new custom designed system or machine for each and every different polymer activation job; however, the cost would then become prohibitive. This highlights the need for a great flexibility for a polymer activation system or machine, which in turn leads to the need for alternative mechanisms which may be added to or removed from the activating hydraulic circuits according to the then current needs.
One way to satisfy both the greater flexibility and a reduced system cost is to adjust the system to process a greater concentration of polymer. For example, instead of producing an output fluid which is 1% polymer, the system may be adjusted to produce a more concentrated fluid which is 2% polymer. Then, the concentrated 2% outflow may be diluted downstream to become 1% polymer, which would double the volume produced by a relatively small machine, to become the volume of a machine of twice the size, if it was originally designed to process a polymer as a 1% fluid. The activation process continues long after the discharge of the inverted polymer from the system outlet.
Merely adding more water in the primary dilution of a polymer might very likely wash away necessary inverting agents, called "activators" or surfactants which are useful in emulsifying the hydrocarbon carrier. For example, a particular use of a particular polymer might require a tenth percent (0.1) polymer solution, but the polymer would lose necessary chemical components if an effort is made to dilute the polymer this much in a single pass through the system. Once a polymer is inverted, there is little, if any, need for retaining these chemical activators. Therefore, the invention presents the opportunity to invert a polymer solution to, say, one percent. (1.0) Once the polymer is inverted, the solution may be diluted downstream to reduce the one percent solution to become a tenth percent solution. Hence, in this example, with the invention, it is possible to produce a tenth percent solution that could not have been produced heretofore.
Two examples of dilution systems which have been designed with these thoughts in mind are found in Rosenberger's and Brazelton's U.S. Pat. Nos. 4,128,147 and 4,642,222. Each of these patents shows a method of adding dilution water to an inverted polymer as it exits a system, thereby theoretically enabling the system to deliver higher concentrations of polymer which are then diluted to give a greater volume of total output. However, it is thought that each of these patents contain basic design flaws since each subjects activated polymers to abrupt pressure changes or additional mixing once the polymer has reached its extended state. That is the output lines of these patents include pressure regulators and/or mixing devices which will create a higher upstream pressure as compared to a lower downstream pressure. Once a polymer is activated, such a pressure change or additional mixing may cause shear and break the now linear polymer molecule, thereby damaging or destroying the polymer.
According to FIG. 1 of the Rosenberger patent the polymer solution is subject to a pressure drop as it passes through the second fixed flow rate regulator. Brazelton teaches the reduction or increase in the input of polymer flow to his mixing system instead of varying the water flow.